Answer:
(1) The solution of the substance used for whitewashing is calcium oxide also called quicklime with chemical formula CaO.
Quicklime is used for whitewashing as it produces calcium hydroxide (CaOH) when it reacts with water (H2O) and absorbs carbon dioxide (CO2) from the environment, as a result, it produces calcium carbonate (CaCO3) which creates a hard coating on the walls.
(2) It forms slacked lime or calcium hydroxide when the quick lime reacts with water
CaO (s) + H2O (l) → Ca(OH)2(aq).
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